Strawberry-Pistachio Layer Cake

Preheat oven to 350°F (180°C). Spray 3 (8-inch) round cake pans with baking spray with flour. Line bottom of pans with parchment paper.

In the bowl of a stand mixer fitted with the paddle attachment, beat butter and sugar at medium speed until fluffy, 3 to 4 minutes, stopping to scrape sides of bowl. Add eggs and egg whites, one at a time, beating well after each addition.

In a medium bowl, whisk together flour, ground pistachios, salt, and baking powder. In a small bowl, whisk together buttermilk, extracts, and food coloring (if using). With mixer on low speed, gradually add flour mixture to butter mixture alternately with buttermilk mixture, beginning and ending with flour mixture, beating just until combined after each addition. Divide batter among prepared pans (about 519 grams each), and spread smooth with a small offset spatula.

Bake until a wooden pick inserted in center comes out clean, about 30 minutes. Let cool in pans for 10 minutes. Remove from pans, and let cool completely on wire racks.

Spread a thin layer of Roasted Strawberry Swiss Meringue Buttercream on 1 cooled cake layer (about ¼ cup or 42 grams). Place 2 cups buttercream in a pastry bag fitted with a medium round piping tip. Pipe a ½-inch-thick border of buttercream around edge of cake layer. Spread half of Roasted Strawberry Jam within border. Top with second cake layer. Spread a thin layer of buttercream on cake layer; pipe a ½-inch-thick border of buttercream around edge of cake layer. Spread remaining Roasted Strawberry Jam within border. Top with remaining cake layer. Spread a thin layer of buttercream on top and sides of cake. Freeze for30 minutes.

Spread remaining Roasted Strawberry Swiss Meringue Buttercream on top and sides of cake. Garnish with strawberries and chopped pistachios, if desired. Refrigerate in an airtight container for up to 3 days.

In the heatproof bowl of a stand mixer, whisk together egg whites, sugar, salt, and cream of tartar by hand. Place bowl over a saucepan of simmering water. Cook, whisking constantly, until sugar dissolves and an instant-read thermometer registers 160°F (71°C).

Carefully return bowl to stand mixer. Using the whisk attachment, beat at high speed until stiff peaks form and meringue is just warm to the touch, about 10 minutes. Add butter, about2 tablespoons (28 grams) at a time, beating until combined after each addition. (If buttercream breaks or looks loose, beat for 2 to 3 minutes, and the emulsion will come back together.) Beat in vanilla.

With mixer on medium speed, add Roasted Strawberry Jam, 1 tablespoon (19 grams) at a time, beating until well combined. Beat in food coloring (if using). Use immediately, or refrigerate in an airtight container for up to 3 days. If refrigerating, let come to room temperature and re-whip before using.

Preheat oven to 400°F (200°C).

In a 13×9-inch baking dish, stir together strawberries, ¼ cup (50 grams) sugar, and salt until well combined.

Bake until berries are soft and fragrant and have released ample liquid, about30 minutes, stirring every 10 minutes.

Transfer berries and juices to a medium heavy-bottomed saucepan; stir in lemon juice and remaining 1 cup (200 grams) sugar. Cook over medium heat, stirring frequently, until berries are cooked down and liquid becomes thick and syrupy, 15 to 20 minutes.

Transfer mixture to the container of a blender, and blend until smooth. Transfer to a heatproof bowl, and let cool completely. Refrigerate in an airtight container for up to 2 weeks.